The underwater roots of mangroves: an amazing ecosystem.
Mangrove forests cover an area of 15 2000 km2 in tropical and subtropical regions, less than 1 % of the tropical forests and less than 0.4 % of the world forests.
In Cuba, mangroves cover 5 % of the nation’s area with a larger distribution in the southern coast, where the tallest and most exuberant trees can be found. Red, black and white mangroves together with buttonwood are the species that make up such forests. The red mangrove is the prevailing species in the Jardines de la Reina National Park.
Mangrove ecosystems represent a natural capital capable of producing a wide range of goods and services for coastal environments and communities and society as a whole. The conservation of biodiversity is one of the most important, as mangroves are permanent or temporary habitat for many species. Underwater mangrove roots are also important as a habitat. The coastal mangroves anchoring themselves in the mud form spaces for other organisms to find support & shelter. The underwater roots can form overhangs that offer space for coral, sponges, anemones, algae, crustaceans, bivalves, polychaete, bryozoans, hydrozoans, ascidians, fungi, bacteria, protists, viruses and many other organisms. Mangrove roots and lower part of trunks provide substrate for oysters and mussels. Because these animals are filter feeders, they are confined to microhabitat below mean high water and usually only abundant in areas adjacent to open waters.
Five red mangrove sites in the Jardines de la Reina National Park were studied to determine cover of sessile organisms (ascidians, algae, sponges, corals and turf) and stony corals in association with crustose coralline algae in submerged roots. Samplings were carried out by visual censuses. Between 2010 and 2012, 450 roots were surveyed. Cover variation of groups among sites and years was observed, with a prevalence of turf. Eleven species of stony corals were identified. The predominant species were the Mustard hill coral and the Thin finger coral. Coral colonies in association with crustose coralline algae were observed. The stony coral settlement in the submerged roots of mangroves is apparently facilitated by the presence of crustose coralline algae.
To determine cover of sessile organisms in the submerged roots of mangroves, a one-meter long PVC pipe marked every 5 cm was used. Root size and cover was measured. As the stony corals in underwater mangrove roots have not been thoroughly studied, each colony was identified and whether such colony was associated to crustose coralline algae was also established. Eleven species of stony corals were recorded and identified.
The stony coral species identified in the submerged roots of mangrove are also present in the coral reefs of the Jardines de la Reina National Park. This is not the same for other groups of organisms occurring in this habitat. In the case of sponges, for instance, only some species can also be found in the Jardines de la Reina reefs. It also happens with macroalgae as some species are typical of the mangrove ecosystems, but due to the high biodiversity, the same species may be found in both ecosystems.
The stony coral Sea ginger has also been found in the mangrove forests of La Leña keys, in the western province of Pinar del Rio. In the Jardines de la Reina National Park, only a few flat colonies of the Mustard hill coral have previously been reported.
The occurrence of stony corals in the underwater roots of mangroves is apparently associated to the presence of crustose coralline algae, besides the physical factors of every mangrove area. Mangroves are not only habitat to many fish, crustacean and mollusk species but to important sessile organisms as well.